On Wed, 22 Jan 2020 07:35:55 -0600, amdx wrote:
If that is so, where would a 300MHz signal originate in the house?
2nd harmonic of the ingress test function in his tester. Some CATV
testers can generate test carriers to help check for cable leakage. It
can also be generated at the CMTS (cable modem termination system).
Helicopters are used to fly over the cable looking for leaks. The
pilot frequency is usually about 140 MHz
Another possible is the 3rd harmonic of a local FM broadcast
transmitter. The harmonic need not be generated in the FM
transmitter, but could simply be caused by a non-linear device in the
cable system generating the harmonic. It also doesn't need to be
generated in the house and could enter the cable (ingress) anywhere
along the cable line. Look for loose or rotten connectors and read
about ingress in CATV systems. The tech should have unplugged the
house cable system from the network to see if the 300MHz signal was
still there. If it goes away, it's being generated in the cable
system. If it's still there, it's either in his unspecified model
tester, a local radio/TV station, or being generated by something in
the house. Try turning off electronics and see what happens.
The coax was connected to the Modem/router on one end and the spectrum
analyzer? on the other end. Could the Modem/router generate a 300MHz signal?
Yes. The reverse (upstream) channel is usually 5-50MHz. You could be
looking at harmonics from that. However, that's unlikely. Some cable
modems use channels at the high end of the spectrum (1000MHz) for
upstream, but those probably won't produce 300MHz.
The last test was testing the speed at the end of the cable where it
would go into the router, Good.
Ok, so you have a "leak" in the cable somewhere in the house. Tear
apart the system and try to isolate the bad segment. The most likely
culprits are the F connectors. Pull on the F connector. If it falls
apart or disconnects from the coax, it's defective. Make sure that
your cables are all RG-6/u and not RG-59/u which tends to be old and
awful. Use push-on connectors (that require a push on tool to install
properly), and not the ring crimp type.
http://www.learnbydestroying.com/jeffl/antennas/Misc/slides/CATV-tools.html
Cable guy left without fixing anything, said the signal strength
should read -9 to +10, and it was 9.1. I ask if that could overload
the input of the modem and cause it to be slow. He just kinda shrugged
and said he wasn't sure.
Would overloading the input of a modem cause it be slow?
Yes. The front end of the cable modem has an AGC (automagic gain
control) that has signal level limits that should be observed. Too
much signal will result in signal distortion. It's easy enough to
build or buy a F-connector type attenuator, and add it in line at the
modem. Start with 3dB or maybe 6dB. I've never had anything improve
with less signal, but it's worth a try.
Cable guy did suggest he try a new modem.
Thanks for reminding me about my favorite rant for this newsgroup.
Is there some reason you conveniently left out most numbers that could
be of use in diagnosing the problem? Is it because you've been
reading Cuisitor Doom's posting and using them as a template? Perhaps
you prefer vague and general answers instead of specifics? I think
you get the idea. Kindly disclose:
1. Type of coax cable used in the house. If it's RG-59/u, your
neighbor will not like my recommendation.
2. Model number of the cable modem.
3. Maker and model number of the tester used.
4. CATV company name.
5. DOCSIS 2.0, 3.0, or 3.1? From your stated speeds, my guess(tm) is
DOCSIS 3.0
While your at it, are you doing the speed tests with a wired ethernet
connection, or are you trying to do it via wireless? Wireless is
often slower than your cable speed and is subject to interference from
other wi-fi systems. Use a CAT5 cable (and a fast computah).
I'm going to try a few things before he spends his money.
Mikek
Cable modems are fairly cheap. Cable gateways, which include a
router, wi-fi, switch, etc, are more expensive and difficult to find
legally. This is what I like and which might work if approved by the
cable ISP:
https://www.newegg.com/arris-sb6190-cable-modem/p/N82E16825694017
However, since he's your neighbor, you could probably remove his
modem, and temporarily replace it with yours and see if it makes a
difference. If nothing changes, then replacing the modem will
probably not do anything useful.
Check the power supply on the modem. I've seen those deterioriate
over the years and produce some really bizarre symptoms.
For signal levels, if the modem is by Arris/Motorola, point your web
browser to 192.168.100.1 and you'll get some signal level diagnostics.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558